Software rejuvenation is a proactive fault management technique that has been extensively studied in the recent literature. In this paper, we focus on an example for a telecommunication billing application considered in Huang et al. (1995) and develop the discrete-time stochastic models to estimate the optimal software rejuvenation schedule. More precisely, two software availability models with rejuvenation are formulated via the discrete semi-Markov processes, and the optimal software rejuvenation schedules which maximize the steady-state availabilities are derived analytically. Further, we develop statistically non-parametric algorithms to estimate the optimal software rejuvenation schedules, provided that the complete sample data of failure times are given. Then, a new statistical device, called the discrete total time on test statistics, is introduced. Finally, we examine asymptotic properties for the statistical estimation algorithms proposed in this paper through a simulation experiment.

Rate control regulates the coded bit stream to satisfy certain given bit rate condition while maintaining the quality of coded video. However, most existing rate control algorithms for low bit rate video can not handle scene change properly, so visual quality is consequently worsened. The test model TMN8 of H.263+ can be forced to skip frames after an abrupt scene change. In this letter, we propose a new frame-layer rate control which allocates bits to frames and controls the frame skipping adaptively based on the pre-analysis of future frames. Experimental results show that the proposed control method provides an effective alternative to existing frame skipping methods causing the motion jerkiness and quality degradation.

We expect that most cellular phones and notebook computers will have Bluetooth in the near future. Many convenient applications will flourish. An example is exchanging multi-media electronic name cards using cellular phones. Today, most people carry a cellular phone. If the user interface can be made as simple as handing out a printed business card, the electronic cards exchanged over Bluetooth would make printed ones obsolete. However the current Bluetooth specification is not adquate to support short peer-to-peer transactions requiring symmectric user interface and fast response time. Connection establishment can take more than 10 s and two devices must start in an asymmetric manner. In this paper, we propose a random inquiry procedure tailored for name card exchange. It allows a symmectric user interface, and device discovery completes within 280 ms with probability 0.999. With this performance, it then becomes practical to provide a hot button on cellular phones that users will simply press to exchange electronic name cards.

The objective of this study was to explore suitable spatial filters for inverse estimation of cortical potentials from the scalp electroencephalogram. The effect of incorporating noise covariance into inverse procedures was examined by computer simulations. The parametric projection filter, which allows inverse estimation with the presence of information on the noise covariance, was applied to an inhomogeneous three-concentric-sphere model under various noise conditions in order to estimate the cortical potentials from the scalp potentials. The present simulation results suggest that incorporation of information on the noise covariance allows better estimation of cortical potentials, than inverse solutions without knowledge about the noise covariance, when the correlation between the signal and noise is low. The method for determining the optimum regularization parameter, which can be applied for parametric inverse techniques, is also discussed.

We present a physics-based circuit simulator employing the Monte Carlo (MC) particle technique, which serves as a bridge between the small-device physics and the circuit designs. Two different geometries of GaAs-MESFET's are modeled and analyzed by the simulator. The Y-parameters of the devices are extracted from the transient currents, and then translated into the S-parameters. The cut-off frequency (fT) is estimated from the Y-parameters. The minimum noise figure (Fmin) is also estimated by evaluating the fluctuation in the stationary current. The device, having the n+-region placed just at the drain side of the gate, exhibits the better performances in both fT and Fmin. The analysis on the equivalent circuit (EC) elements reveals that its better performances are mainly due to the reduced gate-source capacitance (Cgs) and the increased transconductance (gm0), which result from the shortened effective gate length (Lg) caused by the termination of the depletion region at the gate edge. The termination of the depletion region, however, causes the increase of the electric field, which results in the higher heat generation rate near the gate edge. It is proven that the physics-based circuit simulator developed here is fully effective to see the inside of the small-device and to model it for the millimeter-wave circuit design.

This paper defines a new kind of a mixture density model for modeling a quasi-stationary Gaussian process based on mel-cepstral representation. The conventional AR mixture density model can be applied to modeling a quasi-stationary Gaussian AR process. However, it cannot model spectral zeros. In contrast, the proposed model is based on a frequency-warped exponential (EX) model. Accordingly, it can represent spectral poles and zeros with equal weights, and, furthermore, the model spectrum has a high resolution at low frequencies. The parameter estimation algorithm for the proposed model was also derived based on an EM algorithm. Experimental results show that the proposed model has better performance than the AR mixture density model for modeling a frequency-warped EX process.

This paper proposes a novel extraction method of line parameters for multi-coupled lines on high-speed and high-density PCBs, where it uses TDR measurement in time domain and S-parameter measurement in frequency domain. The accuracy of the proposed method have been verified experimentally by comparing the crosstalk noise in the time domain, where (1) the proposed method extracts RLGC matrices by measuring the test pattern, (2) the crosstalk noise is obtained through SPICE simulation using the extracted RLGC matrices, and (3) the SPICE-simulated crosstalk noise is compared with the measured crosstalk noise. From the crosstalk noise comparison, the proposed method is proven to be very accurate. For N-coupled lines, the proposed method doesn't require expensive 2N-port probe for N-coupled lines but only two-port probe, which provides a simple, accurate, and economic extraction method of line parameters for multi-coupled line on the PCB. In the early stage of PCB design, the proposed method is very useful, because it extracts accurate interconnection parameters of each test board and enables to compensate various side effects due to the variation of PCB fabrication process. Also, the proposed method is necessary to analyze the signal integrity of future high-density and high-speed digital system on PCBs.

Microwave Power Transmission (MPT) technology is one of the most essential parts for Solar Power Station/Satellite (SPS). We study on application of magnetrons as DC-RF converters for the MPT transmitting system. Magnetrons cost much cheaper, have much higher DC-RF efficiency over 70% and much lighter system weight per 1 watt RF output than semiconductor amplifiers although they have wider bandwidth of the fundamental frequency and spurious noises in various frequencies. Spurious noises are radiated from the transmitting system and interfere in the other communication systems both in space and on the Earth. The objective of this study is the improvement of the spurious noises generated from magnetrons. Experimentally, magnetrons driven by DC stabilized power supply had not only narrower bandwidth of the fundamental frequency but also lower spurious noise levels when filament current is turned off than when it is turned on. Some spurious noises are probably caused by the intermodulation between the low frequency spurious noises, which frequency is below 1 GHz, and the fundamental or the harmonics. We also verified that the harmonics levels of the measured magnetron in our measurement system were below -70 dBc, which are comparable to or better than those of some semiconductor amplifiers, and that the harmonics were not improved greatly when the filament current was turned off because the source of the harmonics is the distortion of the fundamental.

There have been numerous studies on the enhancement of the noisy speech signal. In this paper, we propose a completely new speech enhancement method, that is, a filtering of a dissonant frequency based on improved fundamental frequency estimation which is developed in frequency domain. The subjective test results indicate that the proposed method provides a significant gain in audible improvement especially for speech contaminated by colored noise and a husky voice. Therefore if the filter is employed as a pre-filter for speech enhancement, the output speech quality and intelligibility should be greatly enhanced.

Utilizing a macromodel which calculates the floating gate potential by combining resistances and dependent voltage and current sources, DC transfer characteristics for multi-input neuron MOS inverters and for those in the neuron MOS full adder circuit are simulated both at room temperature and at 77 K. Based on the simulated results, low temperature circuit failures are discussed. Furthermore, circuit design parameter optimization both for low and room temperature operations is described.

In this paper, we propose an efficient requantization method for transcoding of MPEG video. Transcoding is the process of converting a compressed video format to another different compressed video format. We propose an simple and efficient transcoding by requantization in which MPEG coded video at high bit-rate is converted into MPEG bitstream at lower bit-rate. To reduce a image quality degradation, we use HVS (Human Visual System). By using this effect, the part of image in high activity region is coarsely quantized without seriously degrading the image quality. Experimental results show that the proposed method can provide good performance.

A simple modeling technique for symmetric inductors is proposed. Using the proposed technique, all model parameters for an equivalent circuit of symmetric inductors are easily calculated from geometric, process and substrate resistance parameters without using electromagnetic (EM) simulators. Comparison of simulated results with measured results verifies the effectiveness of the proposed modeling technique up to 5 GHz with center-tapped or non-center-tapped configurations.

An effective method for lossless video compression using intra-frame coding algorithms is described. Intra-frame coding is mainly used for still image compression and does not exploit a temporal correlation in video sequences. With the proposed method, multiple frames are combined into one large picture by interleaving all pixel data. In a large generated picture, the temporal correlation of the video sequence is transformed into a spatial correlation. A large picture enables images to be coded more efficiently and decreases the bitrate for lossless coding using intra-frame coding. We demonstrated the effectiveness of this method by encoding video sequences using JPEG 2000 and JPEG-LS.

Two implementation schemes for a two-step SOVA (Soft Output Viterbi Algorithm) decoder are proposed and verified in a chip. One uses the combination of trace back (TB) logic to find the survivor state and double trace back logic to find the weighting factor of a two-step SOVA. The other is that the reliability values are divided by a scaling factor in order to compensate for the distortion brought by overestimating those values in SOVA. We introduced a fixed scaling factor of 0.25 or 0.33 for a rate 1/3 and designed an 8-state Turbo decoder with a 256-bit frame size to lower the reliability values. The implemented architecture of the two-step SOVA decoder allows important savings in area and high-speed processing compared with the one-step SOVA decoder using register exchange (RE) or trace-back (TB) method. The chip is fabricated using 0.65 µm gate array at Samsung Electronics and it shows higher SNR performance by 2 dB at the BER 10-4 than that of a two-step SOVA decoder without a scaling factor.

This paper deals with a design problem of a robust controller which achieves not only robust stability but also a performance robustness for linear systems with structured uncertainties satisfying matching condition. The performance robustness means that comparing the transient behavior of the uncertain system with a desired one generated by the nominal system, the deterioration of control performance is suppressed. In this approach, the control law consists of a state feedback with the fixed gain designed by using the nominal system, a state feedback with an adaptive gain determined by a parameter adjustment law and a compensation input for the purpose of keeping transient behavior as closely as possible to the desirable one. We show the parameter adjustment law in order to guarantee robust stability and that the condition for the existence of the compensation input is equivalent to the Riccati equation for the standard linear quadratic control problem. Finally, numerical examples are presented.

We propose a method for camera calibration based on image registration. This method registers two images; one is a real image captured by a camera with a calibration object with known shape and texture, and the other is a synthetic image containing the object. The proposed method estimates the parameters of the rotation and translation of the object by using the depth information of the synthetic image. The Gauss-Newton method is used to minimize the residuals of intensities of the two images. The proposed method does not depend on initial values of the minimization, and is applicable to images with much noise. Experimental results using real images demonstrate the robustness against initial state and noise on the image.

Several lifting implementation techniques for invertible deniterlacing are proposed in this paper. Firstly, the invertible deinterlacing is reviewed, and an efficient implementation is presented. Next, two deinterlacer-embedded lifting architectures of discrete wavelet transforms (DWT) is proposed. Performances are compared among several architectures of deinterlacing with DWT. The performance evaluation includes dual-multiplier and single-multiplier architectures. The number of equivalent gates shows that the deinterlacing-embedded architectures require less resources than the separate implementaion. Our experimental evaluation of the dual-multiplier architecture results in 0.8% increase in the gate count, whereas the separate implementation of deinterlacing and DWT requires 6.1% increase from the normal DWT architecture. For the proposed single-multiplier architecture, the gate count is shown to result in 4.5% increase, while the separate counterpart yields 10.7% increase.

An automatic LSI package lead inspection system for backside lead specification is proposed. The proposed system inspects not only lead backside contamination but also the mechanical lead specification such as lead pitch, lead offset and lead overhangs (variations in lead lengths). The total inspection time of a UQFP package with a lead count of 256 is less than the required time of 1 second. Our proposed method is superior to the threshold method used usually, especially for the defect between leads.

The proposed medium access protocol deals especially with the timely-transmission of real-time packets in wireless multimedia networks where users of many types of traffic are present. It works based on Time Division Multiple Access/Time Division Duplex (TDMA/TDD) technique and fixed-length packet switching incorporating two different policies to work differently on either non-congestion or congestion periods. In the policy to deal with congestion periods the concept of urgent packet has been introduced as any packet whose transmission deadline is on the next frame. Hence, during periods of congestion users inform to the Base Station the number and average deadline of the urgent packets in their buffers through requirement messages. According to that information the system is able to distribute its resources in a more efficient way during periods of congestion making the real-time packet loss rate decrease considerably. The simulation results show a very good performance of the method in networks where different types of traffic coexist even under high traffic-load conditions. The results also show a good trade-off characteristic between the real-time access delay and the buffer occupancy of non-real time terminals during congestion periods.

In this paper, a novel confidence scoring method that is applied to N-best hypotheses (word candidates) output from an HMM-based classifier is proposed. In the first pass of the proposed method, the HMM-based classifier with monophone models outputs N-best hypotheses and boundaries of all monophones in the hypotheses. In the second pass, an SM (Subspace Method)-based verifier tests the hypotheses by comparing confidence scores. To test the hypotheses, at first, the SM-based verifier calculates the similarity between phone vectors and an eigen vector set of monophones, then this similarity score is converted into a likelihood score with normalization of acoustic quality, and finally, an HMM-based likelihood of word level and an SM-based likelihood of monophone level are combined to formulate the confidence measure. Two kinds of experiments were performed to evaluate this confidence measure on speaker-independent word recognition. The results showed that the proposed confidence scoring method significantly reduced the word error rate from 4.7% obtained by the standard HMM classifier to 2.0%, and in an unknown word rejection, it reduced the equal error rate from 9.0% to 6.5%.